1. Field
The present invention relates generally to communication systems and more specifically to access terminal identification in a communication system.
2. Background
In a cellular wireless communication system, a cell may include multiple sectors. Multiple cells may then define a subnet. When a Mobile Station (MS) or Access Terminal (AT) initiates a communication with a Base Station (BS) or Access Network (AN), a Universal Access Terminal Identifier (UATI) may be used to identify the AT. The UATI is specific to the subnet where the AT is located at origination of a communication, i.e., establishment of a connection. Each AT initiating a communication in a given subnet will be assigned a full UATI having common Most Significant Bits (MSB). The MSB of the full UATI is a subnet identifier or “subnetID.” The Least Significant Bits (LSB) of the full UATI are then unique to each AT. In this way, the MSB of the UATI identifies the subnet and the LSB of the UATI identifies the AT.
A UATI is 128 bits and is globally unique. To derive a shorter identifier based on UTI that is locally unique, a subnet “color code” scheme, herein referred to as “CC,” assigns a color code to each subnet. The CC is an 8-bit number that is locally unique and provides a mapping to the 104 MSBs of the UATIs in the same subnet. For each AT a Long Code Mask (LCM) is generated using the 24 LSBs of the UATI and the CC. Effectively, the 24 LSBs of the UATI identifies the AT within a subnet, while the CC identifies the subnet. In one example, the CC is concatenated with the 24 LSBs of the UATI to form the LCM.
Once a communication is in process the LCM is not changed. When an AT crosses a subnet boundary several problems may occur. As each subnet may include multiple cells, subnets in close proximity may have a same CC. While neighboring subnets are provisioned with the CC to UATI mapping described hereinabove, the AT may travel to a subnet that does not have this mapping information. In this situation, there is ambiguity in determining the full UATI. In another situation, two ATs may originate from different subnets, wherein the subnets have a same CC. If the LSB of UATIs for the two ATs are the same, then the LCM for the two ATs would be the same, and as a result the signals from the two ATs interfere with each other (i.e., would appear as multipath for each other).
There is a need to generate a unique identifier for a remote station in a wireless communication system. There is further, a need for identifier management when crossing sector boundaries in a cellular system while the mobile is on a traffic channel (i.e., connected state). There is a need therefore for a method of accurately identifying a subnet, when crossing a subnet boundary in a wireless communication system. There is further a need to generate non-overlapping masks and identification information to multiple subnets.